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10.4 Channel Assignments

The multiplexer allows the A/D converter to select one of sixteen analog signals. Eight of these channels correspond to port E input lines to the MCU, four of the channels are internal reference points or test functions, and four channels are reserved. Refer to Table 10-1.

Table 10-1 Converter Channel Assignments

 

Channel

Channel

Result in ADRx if

 

Number

Signal

MULT = 1

 

 

 

 

 

1

AN0

ADR1

 

 

 

 

 

2

AN1

ADR2

 

 

 

 

 

3

AN2

ADR3

 

 

 

 

 

4

AN3

ADR4

 

 

 

 

 

5

AN4

ADR1

 

 

 

 

 

6

AN5

ADR2

 

 

 

 

10

7

AN6

ADR3

 

 

 

8

AN7

ADR4

 

 

 

9 – 12

Reserved

 

 

 

13

VRH1

ADR1

14

VRL1

ADR2

 

15

(VRH)/21

ADR3

 

16

Reserved1

ADR4

NOTES:

1.Used for factory testing

10.5Single-Channel Operation

There are two types of single-channel operation. When SCAN = 0, the first type, the single selected channel is converted four consecutive times. The first result is stored in A/D result register 1 (ADR1), and the fourth result is stored in ADR4. After the fourth conversion is complete, all conversion activity is halted until a new conversion command is written to the ADCTL register. In the second type of single-channel operation, SCAN = 1, conversions continue to be performed on the selected channel with the fifth conversion being stored in register ADR1 (overwriting the first conversion result), the sixth conversion overwriting ADR2, and so on.

10.6 Multiple-Channel Operation

There are two types of multiple-channel operation. When SCAN = 0, the first type, a selected group of four channels is converted one time each. The first result is stored in A/D result register 1 (ADR1), and the fourth result is stored in ADR4. After the fourth conversion is complete, all conversion activity is halted until a new conversion command is written to the ADCTL register. In the second type of multiple-channel operation, SCAN = 1, conversions continue to be performed on the selected group of channels with the fifth conversion being stored in register ADR1 (replacing the earlier conversion result for the first channel in the group), the sixth conversion overwriting ADR2, and so on.

MOTOROLA

ANALOG-TO-DIGITAL CONVERTER

M68HC11 E SERIES

10-6

 

TECHNICAL DATA

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